Re: [R] Problem with the grep function

From: Uwe Ligges <ligges_at_statistik.uni-dortmund.de>
Date: Thu 08 Jul 2004 - 17:54:27 EST

Wolski wrote:

> Hi!
>
> For exact matches you can use
> == or is.element.
> To get the indices use which.
>
> e.g. ==
>
>

>>x<-c("a","b","ab")
>>x=="a"

>
> [1] TRUE FALSE FALSE
>

>>which((x=="a")==T)

Note, the "==T" part is superflously (same below).

In grep()'s regular expression, you can also use:

    grep("^b$", nom)
or similar stuff.

Uwe Ligges

> [1] 1
>
> or
>
> e.g. is.element
>
>

>>is.element(x,"a")

>
> [1] TRUE FALSE FALSE
>
>>which(is.element(x,"a")==TRUE)

>
> [1] 1
>
>
> Sincerely
> Eryk
>
>
> *********** REPLY SEPARATOR ***********
>
> On 7/8/2004 at 9:20 AM aubert@inapg.fr wrote:
>
>
>>>>Let me present to you my problem :
>>>>
>>>>I have a character vector x and I would like to  obtain the indices of
>>>>the 
>>>>elements of
>>>>this vector that yielded exactly a match.
>>>>
>>>>For example,  x=nom, pattern="b", I would to obtain 2 because "b" is on
>>>>the 
>>>>second position.
>>>>
>>>>First program :
>>>>nom <- c("a","b","ab")
>>>>grep("b",nom)
>>>>2 3
>>>>
>>>>Then I try the option extended =FALSE (instead of TRUE by default) and I 
>>>>obtain '2 3' a second time.
>>>>
>>>>Please can you help me : How can I obtain only 2 in using the grep
>>>>function 
>>>>(without using the match function).
>>>>
>>>>Thanks you
>>>>
>>>>Julie AUBERT
>>>>
>>>>______________________________________________
>>>>R-help@stat.math.ethz.ch mailing list
>>>>https://www.stat.math.ethz.ch/mailman/listinfo/r-help
>>>>PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html

>
>
>
>
> Dipl. bio-chem. Eryk Witold Wolski @ MPI-Moleculare Genetic
> Ihnestrasse 63-73 14195 Berlin 'v'
> tel: 0049-30-83875219 / \
> mail: wolski_at_molgen.mpg.de ---W-W---- http://www.molgen.mpg.de/~wolski
>
> ______________________________________________
> R-help@stat.math.ethz.ch mailing list
> https://www.stat.math.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html


R-help@stat.math.ethz.ch mailing list
https://www.stat.math.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Thu Jul 08 18:16:42 2004

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